This invention relates to poly(phenylene ether)-polyamide resin compositions which exhibit enhanced properties, such as reduction of die beard growth.
Poly(phenylene ether) resins (referred to hereafter as "PPE") are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Furthermore, the combination of these resins with polyamide resins into compatibilized blends results in additional overall properties such as chemical resistance, high strength and high flow. Examples of such compatibilized blends can be found in U.S. Pat. Nos. 4,315,086 (Ueno, et al); 4,659,760 (van der Meer); and 4,732,938 (Grant, et al). The properties of these blends can be further enhanced by the addition of various additives such as impact modifiers, flame retardants, light stabilizers, processing stabilizers, heat stabilizers, antioxidants and fillers.
PPE-polyamide blends can be prepared by a variety of methods involving intimate admixing of the materials with any additional additives desired in the formulation. Suitable procedures include solution blending and melt blending. Because of the availability of melt blending equipment in commercial polymer processing facilities, melt processing procedures are generally preferred. Examples of equipment used in such melt compounding methods include: co-rotating and counter-rotating extruders, disc-pack processors and various other types of extrusion equipment. In some instances, the compounded material exits the extruder through small exit holes in a die and the resulting strands of molten resin are cooled by passing the strands through a water bath. The cooled strands can be chopped into small pellets for packaging and further handling.
As the compounded material exits the die of the extruder, a small buildup of material forms on the die at the exit holes. The material buildup is commonly referred to as "die beard growth." Over time the beard growth accumulates at the die holes and requires that the extruder operator periodically wipe the die clean in order to avoid having the beard growth material end up with the final product. This cleaning step is burdensome and time consuming and reduces the productivity of the manufacturing process. Moreover the quality of the PPE-polyamide blend product is negatively affected due to some contamination from the beard growth that inevitably ends up with the final packaged product.
It is therefore apparent that a need exists for PPE-polyamide compositions that have a reduction in beard growth and which do not substantially detract from other important properties, such as impact and tensile strength.